[time-nuts] Building a DC Block Thingy....

[Robert Atkinson]

Hi Jason,
The value of the capacitor is not critical in this case, anywhere from
47pF to 0.01uF. The series inductance and possible resonances are more
important. I used a small axial leaded multi-layer ceramic but any type
intended for high frequency de-coupling or RF applications should be OK.
Generally smaller is better. Ideally you would use surface mount devices
on a micro-stripline PCB, but its over-kill where we are only interested
in one frequency. You can't do much better without access to a network
analyser (or a lot of work with simpler equipment) or specialised RF
components.

Robert G8RPI.

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jason Rabel
Sent: 31 July 2007 01:31
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Building a DC Block Thingy....

); SAEximRunCond expanded to false
Errors-To: time-nuts-bounces+robert.atkinson=genetix.com at febo.com RETRY

Robert,

Thanks, that's kind of the method I was thinking. I was just unsure of
the
capacitor to use. I have also seen in schematics where an inductor is
used
in series with the resistor to block the RF from going to ground (and
possibly causing screwy things I suppose).

I'm still waiting for the unit to arrive, when it does then I can figure
out
how I'm going to do all the connections and everything.

Jason


> Hi Jason,
> I had the same issue with a SatSync GPS. I got an old attenuator
(burned
> out or unknown spec), N type in my case but whatever matches your
> splitter. I unscrewed it and removed the resistors. I placed a 0.001uF
> 63V ceramic capacitor between in and out and a load resistor
(calculated
> to draw just above the antenna warning current) between out (Rx side)
> and ground. I did not feel this resistor would affect the signal too
> much, but slipped a ferrite bead over the ground end lead just for
luck.
> It seems to work OK.
> 
> Robert G8RPI.


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